
nav {
    width: 600px;
    margin: 0 auto;
    padding-bottom: 10px;
    border-bottom: 1px solid rgba(0,0,0,.1);
}
nav ul {
    display: flex;
    justify-content: space-around;
}
nav ul li ol li:first-child {
    font-weight: bold;
}
nav ul li ol li:nth-child(n + 2) {
    margin-top: 5px;
}
nav ul li ol li a:hover {
    color: #42b983;
}
nav ul li div a {
    position: relative;
    line-height: 40px;
    padding-bottom: 3px;
}
nav ul li div a.click {
    border-bottom: 3px solid #42b983;
}
nav ul li {
    position: relative;
}
nav ul li ol {
    width: 120px;
    max-height: 200px;
    overflow: auto;
    padding: 10px;
    margin-top: 5px;
    position: absolute;
    left: -80px;
    top: 35px;
    background-color: white;
    border: 1px solid #b0b0b0;
    display: none;
    z-index: 9;
}
nav ul li span {
    display: inline-block;
    vertical-align: middle;
    margin-top: -1px;
    margin-left: 6px;
    margin-right: -14px;
    width: 0;
    height: 0;
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-top: 5px solid #4f5959;
}
